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I am not too familiar in electronics, but I am currently using them for a Computer Science project.

I am connecting an electromagnetic door lock to a SPDT relay, so that the door can stay on NC and then be opened when I power the coil.

The problem is that I don't know how to to power the common pin as the electromagnet requires \$12\ V, 110\ mA\$. The best that I could find is a \$12\ V, 1\ A\$ plug that I don't think will work due to the power differences.

The link to the electromagnet I plan to use: https://uk.banggood.com/DC-12V-60kg-Visible-Installation-Door-Cabinet-Magnetic-Lock-Access-Control-System-p-1241735.html?rmmds=search&cur_warehouse=CN

Any help to do this would be much appreciated.

SamGibson
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Marcel
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    Just because it can supply 1A doesn’t mean it has to... But, check any number of suppliers and you can find other current ratings. – Jon Custer Jun 16 '20 at 15:43
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    A wording that may help. Instead of thinking of yourself as looking for a "12V 110mA" power source, you are looking for a "12V power source that can output 110mA". That wording will help when reading the answers. – Cort Ammon Jun 16 '20 at 17:40
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    Welcome :-) There's nothing wrong with your question, but FYI it is effectively a duplicate of our canonical Q&A on the topic: "[Choosing power supply, how to get the voltage and current ratings?](https://electronics.stackexchange.com/questions/34745/choosing-power-supply-how-to-get-the-voltage-and-current-ratings)". Hope that helps. – SamGibson Jun 16 '20 at 17:59

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The fact that the power supply is rated \$12\ V\$ at \$1\ A\$ only means that the power supply can output up to \$1\ A\$. The actual current output will be based on the requirements of the specific circuit.

If I put to that supply a circuit that draws \$110\ mA\$, as in your case, that supply will output \$110\ mA\$ at \$12\ V\$, which is a little over a watt of power. If I connect a circuit that requires more than \$1\ A\$ to function, that specific supply won't be able to give enough current to the circuit since the maximum current the supply can provide is \$1\ A\$.

So if I want to power a circuit that requires a \$12\ V\$ rail at \$2\ A\$, for example, I'll need a supply which can output more than \$2\ A\$.

In your specific case a \$1\ A\$ supply for a \$110\ mA\$ circuit is well over enough. You could even do it with a much smaller \$0.5\ A\$ supply if all you need is \$110\ mA\$.

SamGibson
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Quiver
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  • Your answer assumes that "power supply" means _regulated_, _constant voltage_ supply. Of course most of the power supplies that you can by these days _are_ regulated, constant voltage supplies, but even so, your assumption hides information that might help the OP to better understand what's going on. – Solomon Slow Jun 16 '20 at 18:43
  • @SolomonSlow Yeah..I'm not really an expert. This answer was migrated from physics SE, there my answer was, I hope, adequate. Here is not so! – Quiver Jun 16 '20 at 19:26
  • Thank you, I did not realise that the supply would drop the amps to what it needed to be. Thank you – Marcel Jun 16 '20 at 19:47